@article{Seidl96Least,
  author = {Helmut Seidl},
  title = {Least and {G}reatest {S}olutions of {E}quations over $\cal {N}$},
  journal = {Nord. J. Comput.},
  year = 1996,
  pages = {41-62},
  volume = {3},
  number = {1},
}